LOESS DEPOSIT IN EASTERN PART OF QINGHAI XIZANG PLATEAU: ITS CHARACTERISTICS AND ENVIRONMENT

Loess deposit is widespreaded in eastern part of Qinghai Xizang plateau. Preliminary studies on loess stratigraphy, chronology, sedimentology and geochemistry show that loess in the plateau is eolian in origin, and loess material is from various kinds of deposits formed mainly in the western part of the plateau and the plateau monsoon is responsible for transportation and deposition of the loess dust. Although loess deposition started as early as in the Middle Pleistocene, most of the loess deposit in the eastern part of the plateau was deposited since the last interglacial. Our study also shows that loess paleosol sequence is one of the best sources from which the history of the plateau monsoon evolution can be derived. Loess stratigraphy shows that there are 11 enhanced summer monsoon events and 11 intensified winter monsoon events before the last interglacial, and the last interglacial glacial cycle also experienced drastic environment change which correlated well with other climate records in the area.